chore: don't update GitGuardian/homebrew-tap/ anymore

[sevbch]

Context

See GitGuardian/homebrew-tap#8.

What has been done

Remove CI job updating ggshield formula on https://github.com/GitGuardian/homebrew-tap.

Validation

Not really possible to validate locally.

PR check list

• As much as possible, the changes include tests (unit and/or functional)
• If the changes affect the end user (new feature, behavior change, bug fix) then the PR has a changelog entry (see doc/dev/getting-started.md). If the changes do not affect the end user, then the skip-changelog label has been added to the PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.87%. Comparing base (6761a1e) to head (d768697).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1079      +/-   ##
==========================================
- Coverage   91.88%   91.87%   -0.02%     
==========================================
  Files         144      144              
  Lines        6066     6066              
==========================================
- Hits         5574     5573       -1     
- Misses        492      493       +1     

Flag	Coverage Δ
unittests	91.87% <ø> (-0.02%)	⬇️

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